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Re: [Sketch] Don't checksum reliable transmissions

From: Blair Zajac <blair_at_orcaware.com>
Date: Sun, 02 May 2010 12:16:04 -0700

On 5/2/10 8:56 AM, Philipp Marek wrote:
> Hello Stefan!
>> The idea is the following: ra_local (and possibly others)
>> are "reliable" in that they won't corrupt transmission.
>> For now, this implies that we don't need to checksum
>> the data again. There might be more shortcuts that
>> can be taken in the future.
> ...
>> With all other patches applied, this saves 15% runtime
>> in 'svn export file://'. However, rev'ing svn_delta_editor_t
>> seems only be feasible in context of 'editor v2'.
> I understand your point, and 15% sound very interesting.
> But I'd like to note that even for local operations it's a nice feature to avoid data
> corruption via software bugs (off-by-one and similar), and over LAN it's nice to have,
> too (eg. because of bugs in switches and routers, see eg.
> http://www.cs.pitt.edu/~kyoungsoo/cs2520/papers/CRC_TCP_Checksum.pdf).
> As the WAN (Internet) uses the same protocols as a LAN (TCP, IP) following that argument
> would mean that the checksum is informational only, and doesn't need to be checked.
> So I'd propose that this would be configurable for the paranoid people (like me, maybe ;-).

Given the size of the patch, reving of the API and that I like the checksum to
always be done, I would just have svn always perform the checksums.

Received on 2010-05-02 21:16:51 CEST

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